2. Field of the Invention
This invention relates to an industrial boiler.
SUMMARY OF THE INVENTION
An object of the invention is to provide a new and improved industrial boiler.
According to one aspect of the present invention we provide an industrial boiler comprising, a combustion chamber having a furnace therein, means for feeding products of combustion from the combustion chamber to a heat exchanger to heat water/steam therein, a pyrolitic retort, means to feed said products of combustion into heat transfer relationship with the retort to pyrolose material therein and means to feed products of pyrolysis from the retort.
Preferably means are provided to feed products of pyrolysis from the retort to the combustion chamber to fire the furnace therein.
The products of pyrolysis which are fed to the combustion chamber may be in the solid, liquid or gaseous state.
According to another aspect of the present invention we provide an industrial boiler comprising an outer continuous shell within which is contained the steam and/or waterspace of the boiler, a combustion chamber including a furnace, a plurality of smoke tubes for passage therethrough of the products of combustion of the furnace, apparatus for feeding solid fuel to the the furnace gate downwardly through the steam and/or water space of the boiler, a burner to feed fluid fuel to the furnace, a pyrolytic retort, means to feed said products of combustion into heat transfer relationship with the retort to pyrolise material in the retort and means to feed products of pyrolysis from the retort.
Preferably means are provided to feed products of pyrolysis from the retort to said solid fuel feed apparatus and/or said burner for fluid fuel.
The pyrolytic retort may be located in the path of the products of combustion between the combustion chamber and the smoke tubes.
Steam produced by the boiler may be fed to an electric generator, for example a turbine generator and preferably mounted on the boiler and exhaust steam from the generator may be fed to a drying apparatus to predry material to be fed to the pyrolytic retort. The electricity produced by the generator can be used to power the electrically operated services of the boiler such as the means for feeding waste material to and through the pyrolytic retort and, for example, it may be used to drive a hogging machine operative to reduce the size of the waste material prior to entry into the pyrolytic retort. The power can also be used for other purposes in the premises or plant in which the boiler is provided.
As the generator can be provided as part of the "package" supplied by the boiler manufacturer, and is preferably mounted on the boiler itself, a customer is provided with a complete operative assembly.
The material to be fed to the pyrolytic retort may comprise waste material, such as domestic refuse, sewage sludge and the like.
Waste material can consist of many different components. It is not convenient to use such waste products directly as fuel in an industrial boiler because of the different characteristics of the fuels. Whilst a boiler can be set up for one particular waste material it is not possible to use the boiler as thus set up for all waste materials and indeed, it is not always possible to obtain a particular waste material having consistent properties.
However, a wide range of waste materials when pyrolysed produce similar products of pyrolysis. Generally most waste materials give rise to a large volume of combustible gas comprising recoverable and marketable constituent gases such as CO, CO.sub.2, H.sub.2 and CH.sub.4, light and heavy oils, which can be used as liquid fuel, and there remains the charred residue or "char fines" of the waste material which can be used as a solid fuel, or for other petrochemical purposes or as a filter media.
These products of pyrolysis are produced consistently irrespective of the characteristics of the waste material and thus provide a convenient fuel for firing an industrial boiler.
By incorporating a pyrolytic retort in an industrial boiler the products of pyrolysis can be fed directly, or indirectly, to the boiler to fire the boiler and the products of combustion are utilised to heat the pyrolytic retort to pyrolise new waste material to provide future fuel for the boiler.
It is preferred that means are provided for conveniently removing the pyrolytic retort or a part thereof from the boiler either for maintenance of the retort or to permit changing of the retort to shorten maintenance intervals or so as to permit convenient introduction into the furnace of the most suitable pyrolytic retort for the waste material to be utilised.
The pyrolytic retort may be arranged to be lifted vertically from the boiler or may be arranged in a transfer mechanism for movement vertically, or, horozontally transversely, of the boiler whereby one pyrolytic retort or part may be removed from the boiler and a second pyrolytic retort or part simultaneously introduced into the boiler.
The output from the pyrolytic retort may be fed to a recovery system wherein the products are seperated to permit of recovery of desired components, for example, tar, light and heavy oils, ammonia and methane. In addition the char fines are recovered from the pyrolytic retort. The char fines, methane and appropriate oils may be used to fire the boiler as described hereinbefore. If desired, one or a combination of these fuels may be used. The materials recovered from the pyrolytic retort which are not used to fire the boiler may be sold. The charred residue may be treated, for example, with high temperature steam, to produce carbon monoxide and hydrogen combinations.
The charred or carbonised residue of pyrolysis can be used for filtration of effluent from sewage treatment plants before discharge and may be regenerated by passing through the pyroliser again. Alternatively the charred residue may be activated by using superheated steam.